One Method, Two Forms.. Please Help!
I must be missing something very easy here...
I have to forms frmMain and frmLogging
frmMain has several methods within it that will be used periodically.
One of the methods is specific to applicatin logging.
I have a list box created within the frmLogging class
When specific chunks of code are executed within the frmMain class, I am attempting to have them write information via lstBox.add. method to the list box on within the frmLogging class.
Ever time I attempt to do something like this (calling methods in one class to access objects in another) I am running in to problems.
The application appears to load fine but when clicking the button on form 1 to add an item to a list box on form2 the following error occurs.
*** Error ***
An unhandled exception of type 'System.NullReferenceException' occurred in WindowsApplication2.exe
Additional information: Object reference not set to an instance of an object.
***End of Error***
The code for my sample app to demonstrate what I am doing is...
***Code***
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
namespace WindowsApplication2
{
///
/// Summary description for Form1.
///
public class Form1 : System.Windows.Forms.Form
{
private System.Windows.Forms.Button button1;
///
/// Required designer variable.
///
private System.ComponentModel.Container components = null;
public static Form2 form2;
public Form1()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent call
//
}
///
/// Clean up any resources being used.
///
protected override void Dispose( bool disposing )
{
if( disposing )
{
if (components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
///
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
///
private void InitializeComponent()
{
this.button1 = new System.Windows.Forms.Button();
this.SuspendLayout();
//
// button1
//
this.button1.Location = new System.Drawing.Point(92, 172);
this.button1.Name = "button1";
this.button1.TabIndex = 0;
this.button1.Text = "button1";
this.button1.Click += new System.EventHandler(this.button1_Click);
//
// Form1
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(292, 266);
this.Controls.AddRange(new System.Windows.Forms.Control[] {
this.button1});
this.Name = "Form1";
this.Text = "Form1";
this.ResumeLayout(false);
}
#endregion
///
/// The main entry point for the application.
///
[STAThread]
static void Main()
{
Application.Run(new Form1());
}
private void button1_Click(object sender, System.EventArgs e)
{
form2.addToDisplayListBox("This is entry 1");
}
}
}
using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
namespace WindowsApplication2
{
///
/// Summary description for Form2.
///
public class Form2 : System.Windows.Forms.Form
{
private System.Windows.Forms.ListBox Display;
///
/// Required designer variable.
///
private System.ComponentModel.Container components = null;
public Form2()
{
//
// Required for Windows Form Designer support
//
InitializeComponent();
//
// TODO: Add any constructor code after InitializeComponent call
//
}
public void addToDisplayListBox(string msg)
{
Display.Items.Add(msg);
Display.TopIndex=Display.Items.Count-1;
}
///
/// Clean up any resources being used.
///
protected override void Dispose( bool disposing )
{
if( disposing )
{
if(components != null)
{
components.Dispose();
}
}
base.Dispose( disposing );
}
#region Windows Form Designer generated code
///
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
///
private void InitializeComponent()
{
this.Display = new System.Windows.Forms.ListBox();
this.SuspendLayout();
//
// Display
//
this.Display.Location = new System.Drawing.Point(44, 36);
this.Display.Name = "Display";
this.Display.Size = new System.Drawing.Size(184, 147);
this.Display.TabIndex = 1;
//
// Form2
//
this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
this.ClientSize = new System.Drawing.Size(292, 266);
this.Controls.AddRange(new System.Windows.Forms.Control[] {
this.Display});
this.Name = "Form2";
this.Text = "Form2";
this.ResumeLayout(false);
}
#endregion
}
}
I'm sure it is something very simple I am missing. Any assistance is VERY much appreciated.
Thank you all for you help.
Bob
BenPosted Dec 3, 2003, 10:24 PM